Download of the eye.

Anatomy & Physiology
Ch. 8: Special Senses
• The somatic senses are receptors
associated with touch, pressure,
temperature & pain
• The special senses are receptors
associated with the senses (touch,
smell, hearing, taste, vision &
equilibrium)
Types of Receptors:
• Chemoreceptors: respond to changes in
[chemicals]
• Pain receptors: respond to tissue
damage
• Thermoreceptors: respond to changes
in temperature
• Mechanoreceptors: respond to changes
in movement or pressure
• Photoreceptors: respond to changes in
light energy
The Eye & Vision:
• The organs of sight are the eyes, the
eyelids, & the lacrimal apparatus
• The eye orbit contains the above
organs & fat, nerves, muscles, &
blood vessels
• The eyelids protect the eye (open &
close)
• The conjunctiva is within the eyelids
that provides mucous (is a mucous
membrane) to wash the eye.
• The lacrimal apparatus contains the lacrimal
gland & a series of ducts that connect the eye
to the nose & throat. This secretes tears.
• This has 2 ducts which collect tears:
– Lacrimal sac flows into the:
– Nasolacrimal duct (empties into nasal
cavity)
• Tears have lysozymes (enzymes that aid in
eye infection prevention)
• There are 6 extrinsic muscles of the eyes,
which allow for movements in all directions.
http://members.aol.com/dcaronejr/ezmed/lacrimal.jpg
The Structure of the Eye:
The Fibrous Layer (outer layer):
– The cornea (a transparent, thin layer of
epithelium that allows for light transmission
into the eye)
– The sclera which is connected to the
cornea (the white part of the eye) which
protects the eyes & is the attachment for
the extrinsic muscles
– The optic nerve is in the back of the eye &
blood vessels which attaches to the sclera.
The Vascular Layer (middle layer):
– Choroid coat which nourishes the tissues
of the eye & provides the pigment
(melanocytes)
– The ciliary body forms the ring around the
front of the eye; these hold the lens
(transparent) in place
– The iris (a muscle) is the colored portion
of the eye (the lens is directly behind it)
– The pupil is the opening of the eye that
responds to light.
• The Sensory Layer (innermost layer):
– The retina which contains the
photoreceptors (visual receptor
cells). This is the inner lining of the
wall.
– The vitreous humor is the jellylike
fluid that maintains the globular
shape of the eyeball; this fills the
posterior cavity of the eye.
• The lens is clear & elastic (flexible) meaning it can
change its shape to focus.
– This is called accommodation.
• The iris separates the anterior chamber (between
cornea & iris) & posterior chamber (between iris &
vitreous body which contains the lens) of the eye.
• Aqueous humor is the watery fluid in the eye.
http://www.google.com/imgres
http://adam.about.com/b/a/eye.jpg
*Refraction is the means of
light bending in the eye.
This is the focusing of an
image.
*There are 2 types of visual
receptors: rods and cones.
*Rods: more sensitive to
light, provide vision in dim
light, produce colorless
vision, & provide general
outlines of vision (less
precise images)
http://www.google.com/imgres
*Cones: provide sharp
images & detect color.
http://www.veriluxstore.com/images/aboutnaturalspectrum/theretina.jpg
The Ear: Hearing & Balance:
• The ear is the hearing organ.
• It contains 3 parts: the external,
middle & internal parts.
• The external ear: 2 parts:
– the auricle (a.k.a. pinna) collects
sounds & directs them through the
external auditory meatus (a.k.a.
external auditory canal).
The middle ear:
– contains the tympanic cavity
– the eardrum (a.k.a. tympanic membrane):
pressure is changed by the entering sound
waves & reproduces vibrations
– the auditory ossicles (3 small bones:) bridge
the eardrum & the inner & transmit the
impulses as they increase the force (amplify)
the force of vibrations.
• Malleus (hammer)
• Incus (anvil)
• Stapes (stirrup)
• There is a tube that connects the inner
ear to the throat. This is the auditory
tube.
• This maintains air pressure on both
sides of the eardrum (enables proper
hearing)
• When there is a change in altitude, the
pressure of the eardrum is off and
hearing is impaired.
• A popping sound in the ear is the result
of pressure equalizing (enabling hearing)
The inner ear:
• contains chambers & tubes referred to as
a labyrinth. This includes:
– 3 semicircular canals which enable
equilibrium
– Cochlea which enables hearing
– The Organ of Corti contains the
hearing receptors & also contains hair
cells.
http://www.google.com/imgres
Equilibrium:
• Static equilibrium is located within
the vestibular apparatus. This is the
maintenance & stability of the head
when the head & body are still.
• Dynamic equilibrium is the balancing
of the head & body during sudden
movement. This is due to the
semicircular canals of the ear.
Static vs. Dynamic
Equilibrium:
http://www.google.com/imgres
13239049_10211072012
98288_79228891
72637122563_n.j
pg
Sense of Smell:
• Olfactory receptors:
chemoreceptors; only work
when chemicals are
dissolved in a liquid (for
stimulation). Smell & taste
work together.
• Olfactory organs:
– located in the nasal
cavity
– contain olfactory
receptors
– Contain bipolar neurons
with cilia
http://www.google.com/imgres
• Gases enter the nasal cavity & are dissolved into watery
fluids for the receptors to detect them.
• Odorant molecules are substances that trigger the
sense of smell.
• Olfactory receptors adapt quickly.
• Anosmia is the partial or complete loss of smell
http://www.google.com/imgres
Sense of Taste:
• The taste organs are the taste buds.
• These are located on the tongue, roof of
the mouth & pharynx.
• They have papillae, tiny elevations that
contain the taste receptors; the cells that
respond are gustatory cells (taste cells).
• These are chemoreceptors & detect
chemicals when dissolved in liquids.
• This fluid is provided by the salivary
glands
http://www.google.com/imgres
• There are 4 types of taste cells:
– Sweet, sour, salty, & bitter
• Some scientists recognize 3
other types:
– Alkaline, metallic & umami
(tasting MSG)
*This
diagram is
not
accurate 
• These receptors adapt quickly.
• Taste is the [stimulating
chemicals]
• Flavor is the taste, odor, texture
(touch), & temperature.
*See site:
• http://theconversation.com/thatneat-and-tidy-map-of-tastes-onthe-tongue-you-learned-inschool-is-all-wrong-44217
http://www.usc.edu/dept/gero/AgeWorks/core_courses/gero500_core/biology_b_lect/images/Tongue1.GIF
http://www.google.com/imgres
• Know the following: Conjunctivitis (pg. 280),
night blindness, colorblindness (pg. 285),
cataracts, glaucoma (pg. 287), myopia,
hyperopia, astigmatism (pg. 290-291),
deafness, otosclerosis (pg. 298), Meniere’s
syndrome, vertigo (pg. 299), olfactory auras
(pg. 301), strabismus, and presbyopia (pg. 303).
• Read Summary, pgs. 304-306.
• Review, pgs. 306-307, #1, 5, 11, 12, 13, 16, 17,
21, 26, 30, & 31. E.C. #37 & 44